Mixtures of fluorescent whitening agents

ABSTRACT

The present invention relates to a mixture of fluorescent whitening agents comprising 20 to 70% by weight of a compound of formula (1), 30 to 80% of a compound of formula (2) and 0.1 to 10% of a compound of formula (3), compositions containing the mixture and the user of the compositions for whitening synthetic fibers, in particular, polyester.

The present invention relates to mixtures of fluorescent whiteningagents based on various isomers of cyano-substituted1,4-bis-styrylbenzenes.

Fluorescent whitening agents are often used in the form of mixtures oftwo or more components, since such mixtures may exhibit a higher degreeof whiteness than that of the sum of the individual components alone.

Thus, for example, GB 2200660 describes mixtures of 2,3′-, 2,4′- and4,4′-dicyano-1,4-bis-styrylbenzenes, although the composition isrestricted by the method of preparation, whilst U.S. Pat. No. 5,695,686describes similar asymmetric mixtures containing further isomers againdue to the process of preparation. Furthermore, DE 19609956 describesextremely complex mixtures containing up to five different isomers ofthe dicyano-substituted distyryl benzenes.

The constitution of such mixtures of the dicyano-substituted distyrylbenzenes is important not only in regard to their whitening effects, butalso with regard to the shade, which may be more or less reddish orgreenish, the desirability being a matter of utmost importance to theend user.

It has now, surprisingly, been found that particularly high degrees ofwhiteness in especially desirable shades are obtained from mixtures offluorescent whitening agents comprising 20 to 70% by weight of acompound of formula

30 to 80% of a compound of formula

0.1 to 10% of a compound of formula

Furthermore, mixtures comprising 30 to 60% by weight of the compound offormula (1), 30 to 60% of the compound of formula (2) and 0.1 to 5% ofthe compound of formula (3) are of particular interest, whist mixturescomprising 35 to 45% by weight of the compound of formula (1), 50 to 60%of the compound of formula (2) and 0.1 to 3% of the compound of formula(3) or, alternatively, 50 to 60% by weight of the compound of formula(1), 35 to 45% of the compound of formula (2) and 0.1 to 3% of thecompound of formula (3) have been found to be most desirable.

The individual components (1) to (3) of the present invention areprepared by condensing terephthalaldehyde with a2-dialkylphosphonomethyl benzonitrile and further condensing theresulting 2-cyano-4′-formylstilbene obtained as intermediate with a 2-,3- or 4-dialkylphosphonomethyl benzonitrile according to the followingscheme:

whereby R represents methyl, ethyl, propyl or butyl, preferably methylor ethyl.

The initial condensation of terephthalaldehyde with a2-dialkylphosphonomethyl benzonitrile is carried out in a lower alcohol,for example methanol, ethanol, n- or isopropanol or n-, sec.- ortert.-butanol, preferably methanol, as solvent and in the presence of analkali metal hydroxide such as lithium, potassium or sodium hydroxide,preferably potassium hydroxide. After reaction, the 2cyano4′-formylstilbene precipitates from the reaction mixture and isisolated by filtration.

The second condensation step is carried out in a dipolar aprotic solventsuch as dimethyl formamide, dimethyl sulphoxide, N-methyl pyrrolidone ortetramethyl urea, preferably dimethyl formamide, in the presence ofstrong base such as a sodium or potassium C₁-C₅-alcoholate, especiallysodium methylate.

However, it is also possible to obtain mixtures of isomers directly bycondensation of terephthalaldehyde with mixtures of isomericdialkylphosphonomethyl benzonitriles.

Further objects of the present invention are the use of the mixtures ofthe three compounds of the formulae (1) to (3) for whitening syntheticfibres, in particular polyester fibres, said compositions containing amixture comprising 20 to 70% by weight of a compound of formula

30 to 80% of a compound of formula

0.1 to 10% of a compound of formula

Furthermore, mixtures comprising 30 to 60% by weight of the compound offormula (1), 30 to 60% of the compound of formula (2) and 0.1 to 5% ofthe compound of formula (3) are of particular interest, whilst mixturescomprising 35 to 45% by weight of the compound of formula (1), 50 to 60%of the compound of formula (2) and 0.1 to 3% of the compound of formula(3) or, alternatively, 50 to 60% by weight of the compound of formula(1), 35 to 45% of the compound of formula (2) and 0.1 to 3% of thecompound of formula (3) have been found to be most desirable.

As is customary with mixtures of fluorescent whitening agents, theindividual components can be processed to the commercial form bydispersing them in a liquid medium, preferably water. This can be doneby dispersing the individual components and then combining thedispersions so obtained. However, it is also possible to mix theindividual components together in substance and then to disperse themjointly. The dispersing operation is carried out in a conventionalmanner in ball mills, colloid mills, bead mills or the like.

The present invention thus further provides brightener compositionscontaining water and, in each case based on the weight of theformulation, from 3 to 25% by weight, preferably from 5 to 15% by weightof the above defined fluorescent whitening agent mixture and also 0 to60%, preferably 5 to 50% by weight, of auxiliaries.

Suitable auxiliaries include, for example, anionic or non-ionicdispersants from the class of ethylene oxide adducts with fattyalcohols, higher fatty acids or alkyl phenols or ethylenediamineethylene oxide-propylene oxide adducts, copolymers of N-vinylpyrrolidonewith 3-vinylpropionic acid, water retention aids, such as ethyleneglycol, glycerol or sorbitol, or biocides.

The mixtures of this invention and the compositions containing them aresuitable for whitening textile materials made from synthetic fibres, inparticular, those made from linear polyesters. However, these mixturesand compositions can also be used for whitening blends that containlinear polyesters.

The mixtures of this invention are applied by the methods normallyemployed for the application of fluorescent whitening agents, forexample, by the exhaust dying process in dying machines or bypad-thermofixation. The treatment is conveniently effected In an aqueousmedium in which the compounds are present in finely particulate form assuspensions, microdispersdions or, as the case may be, solutions. Ifappropriate, dispersants, stabilisers, wetting agents and otherassistants can be added during the treatment. The treatment is normallycarried out in the temperature range from about 20° C. to 140° C.,preferably 110 to 130° C., for example, at the boiling temperature ofthe bath or in the proximity thereof. Where the mixtures are applied bythe pad-thermofixation process, the thermofixing is preferably carriedout at a temperature of between 170 and 200° C.

The following Examples serve to illustrate the invention; parts andpercentages are by weight, unless otherwise stated.

A. PREPARATIVE EXAMPLES Example 1: 2 Cyano-4′-formylstilbene

Under an atmosphere of nitrogen, a 1.5 l. flask is charged with 480 ml.of methanol and 43.4 g. of 85% potassium hydroxide powder are added withstirring. The potassium hydroxide dissolves and the temperature rises to43° C. The colourless solution is cooled to 2° C. and 82.1 g. of 98%terephthataldehyde added. To the resulting clear solution, a solution of144.8 g. of 2-dimethylphosphonomethyl-benzonitrile in 120 ml. ofmethanol is added dropwise with stirring and cooling over 2 hours at 2°C. After stirring for 2 hours at 2° C., the temperature is raised to 25°C. and the mixture stirred for a further 2 hours. Subsequently, thetemperature is raised to 40° C. and stirring continued for a further 2hours at this temperature. The mixture is then diluted with 180 ml. ofmethanol and the suspension stirred at room temperature overnight. Theprecipitate is then filtered with suction, washed with 2 portions of 250ml. of methanol and sucked dry. There are obtained 140 g. of moistfilter cake, corresponding to 78.3 g. of dry 2-cyano-4′-formylstilbene.

Example 2

Under an atmosphere of nitrogen, a 1.5 l. flask is charged with 100 ml.of methanol and 360 ml. of N,N-dimethyl formamide and 131.8 g. of3-dimethylphosphonomethyl-benzonitrile and 115.2 g. of moist filter cakeobtained in Example 1 added successively. The suspension is warmed to40° C. and 99.0 g. of a 30% solution of sodium methylate in methanoladded dropwise with cooling over 40 min. at 40 to 44° C. Initially, ared solution results. After 10 minutes of the addition spontaneouscrystallisation takes place and the temperature rises temporarily to 49°C. The resulting suspension is then stirred for a further 4 hours at 40to 43° C. and then overnight at room temperature. After dilution with400 ml. of methanol, the mixture is rendered neutral to phenolphthaleinby the addition of 1.0 g. of 100% formic acid, cooled to 0° C. andfiltered. The filter cake is washed with 2 portions of 250 ml. ofmethanol. After drying at 70° C. under vacuum, there are obtained 89.0g. of a yellowish product of formula (1).

By substitution of 3-dimethylphosphonomethyl-benzonitrile in the aboveExample 2 by 4- or 2-dimethylphosphonomethyl-benzonitrile thecorresponding compounds of formula (2) and (3) may be obtained in ananalogous manner.

B. APPLICATION EXAMPLES

a) Exhaust Process

A polyester fabric (Terylene type 540) is treated, in a dying apparatus,at room temperature and at a liquor ratio of 1:20, with an aqueous bathcontaining 0.1% by weight of a mixture of the optical brightening agentsof formula (1), (2) and (3) in the ratios given in Table 1, in finelydispersed form and in the presence of 1 g/l. of a fatty alcoholpolyglycol ether as dispersing agent. The temperature is raised fromroom temperature to 110 over 30 minutes, held for a further 30 minutesat this temperature and subsequently cooled to 40° C. during 15 minutes.The textile material is then rinsed for 30 seconds under running waterand dried at 70° C.

The so-treated polyester fabric exhibits a high degree of whiteness, asmeasured according to Ganz (see Table 1), with a neutral bluish shade.

b) Pad-thermofixation Process

A polyester fabric (Terylene type 540) is treated at room temperature bythe pad-batch process with an aqueous liquor containing 1.2 g/l % of amixture of the optical brightening agents of formula (1), (2) and (3) inthe ratios given in Table 1, in dispersed form and in the presence of 1g/l of an alkali salt of a sulfonated dicarboxylic acid alkyl ester. Thepinch-off effect is 65%. Subsequently, the fabric sample is dried for 30minutes at 70° C. and then thermofixed during 30 seconds at 180° C.

The so-treated polyester fabric exhibits a high degree of whiteness, asmeasured according to Ganz (see Table 1), with a neutral bluish shade.

TABLE 1 White- White- ness ness Compound Compound Compound ProcessProcess Example (1) % (2) % (3) % a) b) 3 39.4 60.0 0.6 215 210 4 59.240.0 0.8 216 212

What is claimed is:
 1. A mixture of fluorescent whitening agentscomprising 30 to 60% by weight of a compound of formula

30 to 60% of a compound of formula

0.1 to 3% of a compound of formula


2. A mixture according to claim 1 comprising 35 to 45% by weight of thecompound of formula (1), 50 to 60% of the compound of formula (2) and0.1 to 3% of the compound of formula (3).
 3. A mixture according toclaim 1 comprising 50 to 60% by weight of the compound of formula (1),35 to 45% of the compound of formula (2) and 0.1 to 3% of the compoundof formula (3).
 4. A composition, which contains water, a mixture offluorescent whitening agents according to claim 1 and, optionally,auxiliaries.
 5. Compositions according to claim 4 containing water and,in each case based on the weight of the formulation, from 3 to 25% byweight of the above defined fluorescent whitening agent mixture and also0 to 60% by weight of auxiliaries.
 6. Compositions according to claim 4containing water and, in each case based on the weight of theformulation, from 5 to 15% by weight of the above defined fluorescentwhitening agent mixture and also 5 to 50% by weight of auxiliaries.
 7. Amethod of whitening synthetic fibres, which comprises contacting thefibers with an effective whitening amount of a mixture according toclaim
 1. 8. A method according to claim 7 wherein the synthetic fibresare polyester fibres.